1. Technical Field
The disclosure relates to an earphone structure, and particularly to a dual-frequency coaxial earphone.
2. Related Art
As shown in FIG. 1, a conventional earphone casing A10 has a signal cable A1, a vibrating diaphragm A2, a permanent magnet A3, a voice coil A4, a magnet conducting member A5 and a yoke A6 assembled therein. The voice coil A4 is assembled on the vibrating diaphragm A2 and encloses a periphery of the permanent magnet A3. A radial gap is defined between the voice coil A4 and the magnet conducting member A5. The permanent magnet A3 is sandwiched between the magnet conducting member A5 and the yoke A6.
The signal cable A1 is connected electrically to the voice coil A4. When an acoustic signals are inputted to the voice coil A4 via the signal cable A1, the voice coil A4 generates a magnet field via electromagnetic effect firstly, and then the magnet field is interacted with the magnet conducting member A5 via magnetic forces so as to drive the vibrating diaphragm A2 to vibrate, so that the acoustic signals are converted to acoustic waves for output.
As in the conventional earphone, generally the acoustic signals includes high frequency acoustic signals and low frequency acoustic signals, so both the high frequency acoustic waves and the low frequency acoustic waves will be generated when the vibrating diaphragm A2 vibrates. However, since the high frequency acoustic waves and the low frequency acoustic waves have different wavelengths and amplitudes, the characters of the two different acoustic waves cannot be distinguished by only one vibrating diaphragm A2, so that in a conventional earphone, the high frequency acoustic waves and the low frequency acoustic waves has intermodulation distortion drawbacks thereby the voices cannot be presented clearly. Although some earphone manufacturers want to assemble the high frequency speaker and the low frequency speaker into the conventional earphone so as to output the high frequency acoustic waves and the low frequency acoustic waves individually, the size of the conventional earphone is not appropriate for such modification.